U.S. patent application number 16/264978 was filed with the patent office on 2019-05-30 for network system for reliable reception of wireless audio.
This patent application is currently assigned to Sound Devices LLC. The applicant listed for this patent is Sound Devices LLC. Invention is credited to Matt Anderson.
Application Number | 20190166423 16/264978 |
Document ID | / |
Family ID | 66632894 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190166423 |
Kind Code |
A1 |
Anderson; Matt |
May 30, 2019 |
NETWORK SYSTEM FOR RELIABLE RECEPTION OF WIRELESS AUDIO
Abstract
Methods and devices are provided for a wireless microphone
network whereby robustness for reception of audio information
transmitted by one or more wireless microphones is enhanced. The
system incorporates a dual stage approach for collecting,
transmitting and receiving audio information. In the first stage,
audio information collected by one or more microphone modules is
transmitted to a series of receiver base stations. In the second
stage, information received at each base station is subsequently
transmitted to a receiver hub that selects, blends and/or augments
the information to produce a high quality representation for audio
information that provides improved robustness and reliability with
respect to the movement, physical placement or performance of each
microphone module.
Inventors: |
Anderson; Matt; (Madison,
WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sound Devices LLC |
Reedsburg |
WI |
US |
|
|
Assignee: |
Sound Devices LLC
Reedsburg
WI
|
Family ID: |
66632894 |
Appl. No.: |
16/264978 |
Filed: |
February 1, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15623522 |
Jun 15, 2017 |
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16264978 |
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62367367 |
Jul 27, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 17/309 20150115;
H04L 65/80 20130101; H04R 2420/07 20130101; H04R 3/005 20130101;
H04R 3/00 20130101; G10L 19/00 20130101; G06F 3/16 20130101 |
International
Class: |
H04R 3/00 20060101
H04R003/00; H04L 29/06 20060101 H04L029/06; H04B 17/309 20060101
H04B017/309 |
Claims
1. A method of connecting a wireless microphone to one or more
endpoints comprising the steps of: providing at least one
microphone module with a transmitting antenna and memory; providing
an array of receiving base stations, wherein each base station has
a receiving antenna, is configured to decode received audio data
into audio over Ethernet data packets and to collect quality of
signal information about the audio data in the respective audio
over Ethernet data packets, is configured to augment the audio over
Ethernet packets with said quality of signal information, and is
further configured to transmit the augmented audio over Ethernet
data packets through an Ethernet connection; providing a receiver
hub configured to receive the audio over Ethernet data packets from
each of the receiving base stations through an Ethernet connection;
connecting the receiving base stations to the receiving hub using
the Ethernet connections to form a second network stage; detecting
a physical audio waveform with the microphone module; wirelessly
transmitting audio data describing the audio waveform through the
transmitting antenna of the at least one microphone over a first
network stage to each receiving base station in the array within
range; continuously receiving the wirelessly transmitted audio data
in at least one of the receiving base stations within range of the
transmitting antenna; in each of the receiving base stations in
range, decoding the received audio data into audio over Ethernet
data packets, collecting quality of signal information about the
audio data and augmenting the respective audio over Ethernet data
packets with said quality of signal information; transmitting the
augmented audio over Ethernet data packets from the receiving base
stations in range over the second stage of the network to be
collected in the receiver hub; reconstructing an output audio
waveform in the receiver hub from the collected audio data in the
augmented audio over Ethernet data packets and based on the
corresponding quality of signal information received from the
receiving base stations in range; and sending or broadcasting the
output audio waveform from the receiver hub to one or more
endpoints.
2. The method according to claim 1, wherein the second stage of the
network is based on Ethernet connections and uses one of the
following audio over Ethernet protocols: DANTE, AES67 and
RAVENNA.
3. The method according to claim 1, wherein the second stage of the
network comprises a wireless connection and data sent over the
second stage is organized into Ethernet frames.
4. The method according to claim 1, wherein the first stage of the
network comprises at least one analog data connection.
5. The method according to claim 1, wherein the first stage of the
network comprises digital data connections.
6. The method according to claim 5, wherein the microphone module
compresses data to reduce the required data bandwidth of the first
stage of the network.
7. The method of claim 1 wherein the microphone module is one of
multiple microphone modules and the receiving base stations and
receiver hub have multiple channels corresponding each to a
respective microphone module.
8. The method of claim 1 wherein the output audio waveform is
constructed on a basis of selecting audio segments corresponding to
base stations wherefrom the lowest error rate occurs after applying
error correction.
9. The method according to claim 1, wherein the quality of signal
information comprises at least one of the number and location of
transmission errors, wireless signal levels, noise levels, signal
to noise ratio, and transmission error rate.
10. The method according to claim 1, wherein the microphone module
stores audio data in a memory buffer and transmits audio data for
one or more previous time periods having a delay of less than about
100 milliseconds when live audio data is transmitted; and further
wherein retransmitted data is available for use when live data is
detected as unreliable and the output audio waveform is suitable
for live broadcast.
11. The method according to claim 1, wherein at times when data
reception is deemed unreliable by a given base station, the base
station mutes the corresponding audio data or sets it to values
known to signify unreliable data, so that unreliable data is
ensured to not be used by the receiver hub.
12. The method according to claim 1, wherein the receiver hub
implements a packet-loss-concealment algorithm to synthesize
missing portions of corrupt data when no valid data has been
transmitted from any of the receiver base stations for a given time
period and the output audio waveform is suitable for live
broadcast.
13. The method according to claim 1, wherein the microphone module
associates the audio data with a time stamp or a sequence
identifier prior to wirelessly transmitting the live audio
data.
14. The method according to claim 10, wherein the microphone module
associates the audio data with a time stamp or a sequence
identifier prior to wirelessly transmitting the live audio data,
and further wherein retransmitted audio data is also associated
with a respective time stamp or sequence identifier.
15. A method of connecting a wireless microphone to one or more
endpoints comprising the steps of: providing at least one
microphone module with a transmitting antenna and memory; providing
an array of receiving base stations, wherein each base station has
a receiving antenna, is configured to decode received audio data
into audio over Ethernet data packets and is further configured to
transmit the audio over Ethernet data packets through an Ethernet
connection; providing a receiver hub configured to receive the
audio over Ethernet data packets from each of the receiving base
stations through an Ethernet connection; connecting the receiving
base stations to the receiving hub using the Ethernet connections
to form a second network stage; detecting a physical audio waveform
with the microphone module, storing audio data in a memory buffer;
wirelessly transmitting audio data describing the audio waveform
through the transmitting antenna of the microphone module over a
first network stage to each receiving base station within range,
wherein the microphone module transmits audio data for one or more
previous time periods when live audio data is wirelessly
transmitted, and further wherein the retransmitted data is
available for use by the system when live data is detected as
unreliable; receiving the wirelessly transmitted audio data in the
receiving base stations within range of the transmitting antenna;
in each of the receiving base stations in range, decoding the
received audio data into audio over Ethernet data packets;
transmitting the audio over Ethernet data packets from the
receiving base stations in range over the second stage of the
network to be collected in the receiver hub; reconstructing an
output audio waveform in the receiver hub from the collected audio
data in the audio over Ethernet data packets; and sending or
broadcasting the output audio waveform from the receiver hub to one
or more endpoints.
16. The method according to claim 15, wherein the microphone module
associates the audio data with a time stamp or a sequence
identifier prior to wirelessly transmitting the live audio data,
and further wherein retransmitted audio data is also associated
with a respective time stamp or sequence identifier.
17. The method according to claim 15, wherein the retransmitted
audio data has a delay of less than about 100 milliseconds.
18. The method according to claim 15, wherein the retransmitted
audio data has a delay of less than about 30 milliseconds.
19. A method of connecting a wireless microphone to one or more
endpoints comprising the steps of: providing at least one
microphone module with a transmitting antenna; providing an array
of receiving base stations, wherein each base station has a
receiving antenna, is configured to decode received audio data into
audio over Ethernet data packets and is further configured to
transmit the audio over Ethernet data packets through an Ethernet
connection; providing a receiver hub configured to receive the
audio over Ethernet data packets from each of the receiving base
stations through an Ethernet connection; connecting the receiving
base stations to the receiving hub using the Ethernet connections
to form a second network stage; detecting a physical audio waveform
with the microphone module, storing audio data in a memory buffer;
wirelessly transmitting audio data describing the audio waveform
through the transmitting antenna of the microphone module over a
first network stage to each receiving base station within range;
receiving the wirelessly transmitted audio data in the receiving
base stations within range of the transmitting antenna; in each of
the receiving base stations in range, decoding the received audio
data into audio over Ethernet data packets; transmitting the audio
over Ethernet data packets from the receiving base stations in
range over the second stage of the network to be collected in the
receiver hub; reconstructing an output audio waveform in the
receiver hub from the collected audio data in the audio over
Ethernet data packets, unless no valid data has been transmitted
from any of the receiver base stations for a given time period in
which case the receiver hub implements a packet-loss-concealment
algorithm to synthesize missing portions of corrupt data; and
sending or broadcasting the output audio waveform from the receiver
hub to one or more endpoints.
20. The method according to claim 19, wherein the given time period
is less than about 30 milliseconds and the output audio waveform is
suitable for live broadcast.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 15/623,522 filed Jun. 16, 2017, which claims
the benefit of U.S. Provisional Application No. 62/367,367 filed
Jul. 27, 2016.
BACKGROUND
[0002] Wireless microphones are commonly used in numerous
recording, playback or broadcast environments, including concerts,
live stage recording, theatre, education, conferences, television
or radio. The microphone modules themselves are often configured as
either handheld or as a smaller lavalier microphone unit that is
connected with a transmitter pack. Audio information collected by
the microphone module is transmitted to and received at a receiver
base-station. The transmitter unit in the microphone module should
be as lightweight as possible, while providing a sufficiently long
lifetime of operation without the need for battery recharging or
replacement while at the same time, providing as wide of a range as
possible for the allowable physical location of the module.
However, the strength of signal received by a base station is
dependent on both the strength (power level) of the transmitted
signal and location of the microphone module relative to the base
station. Accordingly, it is desirable to create a wireless
microphone system with an improved range of reception for a given
transmission power level.
SUMMARY
[0003] The disclosed invention provides a means to improve the
allowable physical range for the operation of a wireless microphone
while maintaining limits on the power levels used for data
transmission between a microphone module and two or more receiving
base stations.
[0004] A microphone module may be worn or carried by a user or
mounted with good proximity to a desired sound source such as a
performer, talker, musical instrument or other acoustic source. In
the case of a wireless microphone module, audio information may be
wirelessly communicated to another location for storage
(recording), playback or broadcast. The efficacy of such a system
depends on reliable transmission of audio data. Tradeoffs in the
design of a wireless microphone module include the size and weight
of the battery, the transmitter output power level, useful battery
life and bandwidth (or transmission data capacity) in order to
maintain reliability of transmission over a sufficient range for
the physical placement or movement of the microphone module.
Extending the allowable range of microphone modules for a fixed or
lower transmitter power level provides an opportunity for using
both a lighter weight battery, reduced power consumption and/or
using a lower power transmitter design and may even aid in helping
make devices compliant with FCC or other government
regulations.
[0005] According to the invention, each microphone module transmits
collected audio information wirelessly through a first stage of the
network to be received by two or more base stations at different
physical locations. Depending on their locations, each of them will
present a distinct level of electromagnetic coupling and noise
level with respect to the current location for each transmitting
microphone module. Therefore, at any given time, the available
received signal strength (or signal to noise ratio) for each module
will vary from one base station to another. Accordingly, depending
on physical placement, one or more base stations will have an
advantage in receiving transmitted audio data over the others. In
some embodiments, each base station may individually determine a
receive signal strength indicator (or RSSI) based on the strength
of their respective receive signal strengths. This information may
then be used in reconstructing the (transmitted) audio waveform.
For example, the output audio waveform may be constructed by
emphasizing audio segments corresponding to base stations reporting
the highest RSSI's or estimated signal to noise levels. In the art,
RSSI refers to a measurement of the power present in a received
radio signal (that is modulated to reside in a channel frequency
and bandwidth). If background noise levels are also either known or
inferred based on other measurements, a signal-to-noise-ratio (or
SNR in dB) can be estimated by subtracting the noise power level
(measured in dBm) from the RSSI level (also assumed measured in
dBm).
[0006] Within the context of the invention utilizing spatial
redundancy, two or more base stations remain operative in
attempting to continue receiving wireless information from a given
microphone module at the same time. These receiving base stations
then each relay all of the audio information (or conditioned data)
they collect, sending it over a secondary stage of the network to
be blended or combined at a receiver hub. An advantage of sending
all receiver information is the ability to exploit other modes of
redundancy to ensure reliable reception, as described later in this
disclosure. In addition to providing opportunities to exploit
spatial redundancy (resulting from distributed receiver locations),
other aspects of this invention may also allow exploiting
opportunities for temporal redundancy (resulting from transmitting
audio data derived from different points in time). In yet further
aspects of this invention, the receiver hub, may be able (since it
receives all receiver data) to identify points in time where no
valid data exists from any receiver base. In these cases, a third
mode of redundancy based on the correlation statistics of the audio
waveform itself may be exploited to synthesize missing portions of
(corrupt) audio data via packet-loss-concealments algorithms
(PLCAs). For example, ITU Recommendation G.711 appendix I specifies
a well known PLCA that is effective for synthesizing periods of
audio data loss spanning up to a few tens of milliseconds.
Particularly, in cases where a high degree of correlation exists in
the audio signal such during voiced periods, a PLCA may render a
gap in audio data unnoticeable to listeners. It is expected that
even with the benefits of a diversity receiver array, periods of
corrupt audio may occur either due to glitches or intermittent
interferences with the microphone. These may include moments when
user bumps or knocks a microphone against a solid object, causing a
sharp and audible "thump" in the resultant data, temporarily
rendering any collected data as corrupt. In instances such as
these, the microphone module may itself condition (or mute) audio
data to signify time (sample) periods when detected audio is
assumed corrupted.
[0007] The secondary stage of the network is preferably either
wired or wireless Ethernet and each base station may process the
audio information they receive preferably into a "Digital Audio
through Ethernet" (DANTE) compatible format before transmitting it
to the receiver hub. In the preferred embodiment, data packets are
encoded based on the DANTE protocol (Layer 3 packets). Other
protocols that do not rely on the Ethernet frame structure (Layer 1
protocols) that may also facilitate communication for the second
stage of the network include: AES50, SuperMAC, HyperMAC, A-Net,
AudioRail, RockNet or Hydra2. Furthermore other protocols relying
on standard Ethernet packets (Layer 2) may include: AES51, AVB,
Ethersound, REAC, SoundGrid, or dSnake. Finally other audio over
Ethernet protocols based on network layer packets (Layer 3) may
include: UDP data packets, AES67, AVB, NetJack, RAVENNA, Livewire,
Q-Lan or WheatNet-IP. Any of these can suffice for communication in
the second stage of the communications network provided each
base-station is equipped for the encoding and broadcast (or
transmission) of data and the receiver hub 105 is equipped for the
decoding and reception of incoming audio data. The receiver hub
collects and analyzes information received from each base stations
to construct the best possible representation of information (audio
waveform) originally detected and sent by the microphone module.
The resultant audio information or constructed waveform is supplies
to one or more endpoints.
[0008] In some embodiments, operations performed by the receiver
hub may include dynamically selecting information sent by the base
station that has the lowest error rate in its decoded audio signal.
In other embodiments, it may select decoded information received by
the base station reporting the highest signal strength from the
microphone module. Other yet other embodiments, the decoded
information from multiple base stations may be blended together
with decoded information from multiple base stations to produce a
decoded signal that is higher quality than what would otherwise be
possible from information received from a single base station.
Based on this, the receiver hub reconstructs and outputs a waveform
or data representing of the original audio signal.
[0009] This resultant output from the receiver station may then be
recorded, broadcast, mixed with other audio sources and/or played
back to listeners via headphone or loudspeaker arrangement. In some
embodiments, the microphone modules themselves will encode audio
waveform data for reduce bandwidth requirements. In these cases,
the step of decoding the data for the actual audio waveform (audio
PCM data) may be performed at either each base station, the
receiver hub or at a later time if this data is to be recorded.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a simplified diagram for wireless microphone
system with a two-stage network in accordance with a first
exemplary embodiment of the present invention, where the secondary
stage is based on a star topology.
[0011] FIG. 2 is an example embodiment including two microphone
modules where the secondary network is based on a serial
topology.
[0012] FIG. 3 is a block diagram showing select steps that may be
taken by a digital microphone module in transmitting audio data
according to an exemplary embodiment.
[0013] FIG. 4 is a block diagram showing select steps that may be
taken for a base station receiving, audio data from the microphone
module, processing that data and forwarding it to a receiver hub
according to an exemplary embodiment.
[0014] FIG. 5 is a block diagram showing select steps that may be
taken for receiving, audio data from each base station by a
receiver hub and processing that data before forwarding it to be
recorded, broadcast or played back according to an exemplary
embodiment.
DETAILED DESCRIPTION
[0015] FIG. 1 shows a system 100 constructed in accordance with an
exemplary embodiment of the invention. In this disclosure, the term
"audio waveform" refers to physical acoustic sound or vibration
present at a given location that is desired to be captured via a
wireless microphone. As shown in FIG. 1, a microphone module 101
includes at least one microphone element 114 for sensing an audio
waveform and a microphone transmitter 102 that contains suitable
electronics and an antenna to be capable of wirelessly transmitting
information or data from the microphone module 101. Normally, the
transmitted information would allow for characterization of or
describing the audio waveform over time. For example, with a
digital wireless microphone, the audio waveform may be converted to
an electrical waveform and digitized using an analog to digital
converter (ADC) at a given sample rate. Audio data representing the
digital samples can be transmitted by the microphone transmitter
102. In some embodiments, data compression may be used for reducing
the data rate required for transmission of the audio waveform. In
the case of an analog wireless microphone, the audio waveform can
be used as a basis for frequency modulating a carrier output from
the microphone transmitter 102. The modulation used for
transmitting wireless audio data from the microphone module 101 may
rely on FM, phase-shift keying (PSK, BPSK, QPSK, etc.) or
spread-spectrum techniques. Other elements not shown that may be
part of the design for the microphone module 101 include a housing
for structural support, various circuits, power supplies,
batteries, adapters, clips, amplifiers, companders, limiters,
signal conditioners or filters, analog to digital converters,
memory, communications circuits, modulators, antennas,
microprocessor, digital signal processors and/or software for
configuration, control and operation of the microphone module 101
that will be apparent to one skilled in the art.
[0016] A series of base-stations placed in the general vicinity of
the microphone module 101 can attempt to receive wireless audio
data being transmitted by it. Each base station includes or is
coupled with a base station receiver. Specifically, a first
base-station 103A is coupled with a first base station receiver
104A, a second base station 103B is coupled with a second base
station receiver 104B through an N.sup.th base-station 103N is
coupled with an N.sup.th base station receiver 104N. Each
base-station receiver includes an antenna and may be placed in the
vicinity of the microphone transmitter 102 (or location where it is
expected to be near at some point in time depending on the
anticipated movement of the microphone module 101). Each
base-station receiver (with its antenna and supporting electronics)
attempts to detect the RF signal modulated by audio data,
demodulate it and retrieve the original audio data that was
transmitted from the microphone module 101 by its microphone
transmitter 102. Each base station will also include the required
internal electronics and/or software as needed to further process
received audio data and transmit it from an attached communications
link, as later described in this disclosure. In some embodiments,
the base station and base-station may be integrated into the same
package/unit. In other embodiments, the base station may be
packaged separately from (although still connected to) its
base-station receiver. Similarly, a microphone module 101 may be
integrated with its transmitter 102 in the same package, or they
may be packaged separately, (although still connected). While a
total of N base-stations are indicated by the diagram, in some
embodiments, only two base stations (N=2) or three (N=3) may be
required. In general, the invention may be flexible in how many
base-stations are used. In the art, wireless microphone systems
that utilize multiple receiving base-stations are often referred to
as "diversity wireless receivers" or are referred to as having
"diversity reception". In the art, diversity reception may improve
the reliability of reception based on redundancy in
bandwidth--where multiple antennas are used simultaneously. In
addition to dual antenna diversity, the invention includes modes
utilizing spatial, correlation and/or temporal redundancy to
improve reliability.
[0017] In FIG. 1, an electromagnetic coupling is drawn between each
base station receiver, 104A, 104B through 104N, and the microphone
transmitter 102. However, the ability for each base station to
receive audio data from the microphone module 101 will in general
depend on the position of the microphone transmitter 102 relative
to the placement of each base station 104A receiver, 104B through
104N. For example, if the microphone transmitter 102 is placed
closer to the first base station 104A receiver and further from
second base station 104B receiver, the first base station receiver
104A may have an advantage in receiving a higher signal-to-noise
ratio (SNR) at its antenna than for the second base station
receiver 104B. Accordingly, in the case of a digital wireless
transmission of audio data from the microphone transmitter 102, the
first base station 103A may be able to accept a higher rate of data
transmission and/or achieve a lower error rate in receiving audio
data from the microphone module 101 than for the second base
station 103B. In the case of an analog wireless transmission of
audio data from the microphone transmitter 102, the first base
station 103A may be able to provide a higher SNR for received audio
data (waveform) than for the second base station 103B.
[0018] In contrast, if at a later time, the microphone transmitter
102 is moved to a position closer to the second base station
receiver 104B than for the first base station receiver 104A, the
second base station receiver 104B may have an advantage in
receiving a higher signal-to-noise ratio (SNR) at its antenna than
for the first base station receiver 104A. Accordingly, in the case
of a digital wireless transmission of audio data from the
microphone transmitter 102, the second base station 103B may be
able to accept a higher rate of data transmission and/or achieve a
lower error rate in receiving audio data from the microphone module
101 than for the first base station 103A. In the case of an analog
wireless transmission of audio data from the microphone transmitter
102, the second base station 103B may be able to provide a higher
SNR for received audio data (waveform) than for the first base
station 103A.
[0019] In general, the SNR with respect to data transmitted by the
microphone transmitter 102 will vary from one base station receiver
to another. While the SNR will depend on the distance between each
base station receiver and the microphone transmitter 102, it may
also depend on electromagnetic interference caused by other objects
or obstructions, the position, spectral content and strength of
other electromagnetic noise/interference sources, and line of sight
between the base-station receiver in question and the microphone
transmitter 102. In some embodiments, the base-stations and their
receivers themselves may not be identical. In these cases, the
received SNR or transmission error rate may also depend on
differences between the antenna and/or amplifiers or other
electronics used within each base-station and its receiver.
[0020] In some embodiments, the location of the microphone
transmitter 102 (and often, the microphone module 101 integrated
with it) may be fixed. For example, it may be mounted on a
microphone stand in front of a performer. In other embodiments, the
microphone transmitter 102 may be moving. For example, it may be
carried by a performer in a live theatre setting. In general,
knowing which base-station receiver, 104A, 104B through 104N will
provide the highest SNR or most reliable data communication link to
the microphone transmitter 102 is generally very difficult to
determine. This depends on a myriad of factors going beyond the
simple location of either the microphone transmitter 102 or any of
the base-station receivers, 104A, 104B through 104N. Furthermore,
in many settings, the index (for example, indexing the first
base-station 104A as "A", the second base-station 104B as "B" and
so on to index the N.sup.th base-station 104N as "N") for the base
station receiver provided the best reception may rapidly change
over time as performers, theatre/stage equipment/props, microphone
modules (and their transmitters), interference sources move about
and in some cases, even the location of the base-stations and their
receivers changes.
[0021] Additionally, the occurrence of errors in the reception of
transmitted audio data are statistical in nature with the exact
timing and number of error for digital transmission of audio data
or details of noise induced for analog transmission of audio data
impossible to predict with respect to each base-station. For
example, even if the microphone transmitter 102 is much closer to
the first base station receiver 104A and provides it with a higher
SNR than for the second base station receiver 104B, there still may
be instances or periods of time when digital transmission errors
occur for reception of data at the first-base station 103A, while
data is properly received by the second base-station 103B. As
another example, if an interference source is placed much closer to
the first base station receive 104A than for the second 104B, the
SNR for reception at the first base station receiver 104A may be
worse than for the second 104B, even if the second base station
receive is farther from the microphone transmitter 102 and present
a lower overall wireless signal level.
[0022] Previous approaches that assign one base-station receiver or
the other to receive wireless audio data from the microphone
transmitter 102 suffer from the fact that when errors or noise
occur for the selected base-station, there may be others that could
have otherwise provided the missing data, having properly received
it or a lower noise level.
[0023] The invention overcomes the important problem of knowing
which base-station is best suited for receiving audio data by
having multiple (or in the preferred embodiment, all) base-stations
continuously receive data from the microphone transmitter 102 and
continuously forward this data to a receiver hub 105, that retains
access to all available valid information over time.
[0024] As shown in FIG. 1, the first base station 104A is provided
with a secondary communications link 109A to a receiver hub 105.
Similarly, the second base-station 104B is provided with a
secondary communications link 109B to a receiver hub 105. This
continues for each additional base-station until the N.sup.th
base-station 104N, being provided with a secondary communications
link to the receiver hub 105.
[0025] As indicated in FIG. 1, the combination of the microphone
transmitter 102, the collection of each path electromagnetically
coupling it to each base-station and each base-station receiver can
be considered as comprising the first stage 115 of a communications
network. This is indicated by a dashed box surrounding these
elements in FIG. 1.
[0026] In contrast, the combination of each communications link,
109A, 109B through 109N and receiver hub 105 can be considered as
comprising a second stage of a communication network 116. This is
again indicated by a dashed box surrounding these elements in FIG.
1.
[0027] Base stations 103A, 103B through 103N can be considered as
bridging the two stages of the communications network, as they
receive wireless audio data from their respective base-station
receivers and re-transmit or broadcast this information over the
communications links, 109A, 109B through 109N. The communications
links 109A, 109B through 109N may be either wired or wireless and
in the preferred embodiment, based on an Ethernet connection. In
these cases, base stations 103A, 103B through 103N preferably
further processes and reformat audio data received by their
respective base-station receivers into a series of internet
protocol (IP) packets (or layer 3 IP packets), where the data
format is based on the "Digital Audio Network Through Ethernet" or
DANTE protocol.
[0028] Upon receiving the audio data re-transmitted from each
base-station, the receiver hub 105 may construct an output data
stream representing the original audio data sent by the microphone
module 101 by augmenting data segments selected from any
base-station that is able to provide those portion on an error-free
basis over time.
[0029] In some embodiments where data is digitally transmitted
between a microphone module 101 and each base-station 103A, 103B
through 103N, the microphone module may digitize the audio waveform
received from the microphone element 114 and subsequently encode it
the data for a reduced data rate. It may furthermore encode the
data utilizing an error correcting code. In some embodiments,
encryption may be additionally applied. For these embodiments, the
receiver hub 105 may construct an error free output data stream by
decoding (and when required, decrypting) the received data and
augmenting data segments where error correction is possible.
Otherwise, in cases where no segments exist that are either
error-free or would allow for complete error correction, the
receiver hub 105 may select segments for output data stream
construction that have the lowest error rate. In cases where error
correction is not used but the data transmission format allows for
error detection, the receiver hub 105 may construct the output data
stream by augmenting data segments selected to have the lowest
number of detected errors.
[0030] In some embodiments, analog data transmission occurs between
the microphone module 101 and each base-station 103A, 103B through
103N. For example, the transmitter 102 of the microphone module 101
may transmit an audio signal based on an analog wideband FM
transmission over a bandwidth of approximately 200 kHz over the
first stage 115 of the network. In these cases, each base station
may digitize, encode and forward the received signals with any
noise artifacts over the second stage of the network 116 to the
receiver hub 105. The receiver hub 105 may then reconstruct a
reduced noise or noise-free output based on the combination of
received data streams. For example it may simply emphasize the
signal corresponding to the base-station reporting the highest
signal level. In some embodiments, it may blend the audio data on a
basis of the signal strength reported from each base-station. For
example, if two base stations are both receiving an analog signal
based on a signal strength that is similar between them, the
receiver hub 105 may construct an output based on an average
between the multiple received audio signals commonly spanning a
given time interval. In some embodiments, the output may be formed
based on a weighted sum of the audio waveform received from each
base station where the weighting is dependent on the signal levels,
SNR or receiver error rate detected at each base station. Finally,
embodiments are envisioned where if several base stations detect a
good signal level, the output may be formed on a basis of outlier
rejection. For example, if at a point in time, the waveforms from
three of the base stations are reported as 0.5, 0.51 and 0.49,
while a fourth base station reports an audio waveform having a
value of 1.5, this value would be rejected as being an outlier.
Other useful functions may be included that are based weighted sums
(on a basis of SNR or RSSI) or median filters applied to the array
of received signal segments received (or collected) from the set of
base stations. In order to facilitate the rejection of faulty data,
each receiver hub may condition its data based on estimated SNR or
quality of reception. For example, if a section of data is known to
be unreliable at a base station, data received by this base station
may be conditioned to signify a low expectation of reliability,
such as muting or zeroing out corrupt audio data. If this audio
data is later reconstructed at the receiver hub, based on weighted
sums, the zero data will have not corrupt a weighted sum or
average. Alternatively, a base station may identify unreliable data
by setting values to a predetermined pattern, such as
alternating+/-full scale so that a receiver hub can easily identify
and omit this data from reconstruction based on outlier rejection
methods.
[0031] The output from the receiver hub 105 may consist of either
an analog audio output, digital audio PCM, compressed digital audio
or other data stream representing the reconstructed audio signal.
It is provided as an input to one or more end-points. Examples of
end-points shown in the system 100 of FIG. 1 include a
mixer/recorder 106, a broadcast network 107 or a playback device
108. Other types of end-points can include virtually any device or
system that could benefit from access to the output data stream and
are envisioned within the scope of this disclosure.
[0032] FIG. 3 illustrate a simplified block diagram showing select
steps that may be taken by a digital microphone module in detecting
a physical waveform and transmitting corresponding audio data
across the first stage 115 of the network according to an exemplary
embodiment.
[0033] At step 310, method 300 includes using a microphone element
114 for detecting a physical sound waveform and converting it to an
analog electrical waveform. Other operations that may be included
in this step include filtering and amplifying this signal and in
the case of an analog wireless transmission, optionally companding
or limiting. In the case of analog wireless transmission, the
process proceeds to step 350. At this step, additional information
may be embedded with each audio segment to indicate the chronology,
timing and/or order of each segment. This information may take the
form of a time-stamp or chronological numbering where sequential
binary numbers are assigned to each segment as they are processed.
Examples of timecodes include SMTPE or linear time code (LTC) or
may be included as part of the DANTE protocol. These may be
generated internally or externally supplied for synchronizing
between audio segments. As another example of time stamps, a timer
value may indicate absolute time-alignment with respect to the
start of a recording. In this case, a sample-period counter/timer
may also be used to indicate an absolute or relative sample-period
index for specific sample (such as the first or last one) in the
segment to be subsequently used for the time-alignment of each
segment. It should be recognized that in some embodiments where
exceptionally low latencies exist (operating in real-time), the
application of timing information may be unnecessary, where the
timing of audio segments is inferred based on the time (and the
order) that they are received. Otherwise, in the case of digital
wireless transmission, the process proceeds to step 320. At this
step, the analog electrical waveform is processed by an analog to
digital converter (ADC). Additional operations that may be included
in this step include digitally filtering or limiting the digitized
audio signal. The process then continues to optional step 330. At
this step, a software algorithm is applied to reduce the required
bit rate for transmission of the digital audio data. Typically, a
low-latency data compression algorithm is preferred having less
than a few milliseconds of delay. The process continues to the next
optional step 340 where depending on the desired data transmission
rate, error correcting codes may be applied to the bit-stream to
improve the robustness to wireless transmission errors. In other
cases, redundant bits may be added to allow for error checking.
Either error correcting codes or error checking will increase the
required transmission data rate, depending on the complexity of the
algorithm. Next, timing or sequence data is embedded if necessary
as discussed previously with respect to block 350. The process
proceeds to step 352 where the digital data stream is converted
into a modulated waveform suitable for RF transmission with timing
information, as needed. The type of modulation may include FM, FSK,
PSK, QPSK or other modulation techniques may be suitable. Other
operations may include signal conditioning, filtering and
amplification of the signal. The process then proceeds to step 360
where the modulated waveform is converted into an electromagnetic
signal transmitted from the microphone module transmitter, 102.
[0034] FIG. 4 illustrate a simplified block diagram showing select
steps that may be taken by a base station in receiving audio data
that is wirelessly transmitted across the first stage 115 of the
network, processing, reformatting and if required, timing and
conditioning the received data for transmission over the second
stage 116 of the network according to an exemplary embodiment.
[0035] At step 410, method 400 includes the base station receiver
detecting the electromagnetic signal for any active channels (with
each channel associated with a microphone module). Additional
operations that may be included in step 410 are amplifying,
filtering and conditioning the received signals. The process
proceeds to step 420 where the received data is demodulated. If the
wireless data is analog, the process proceeds to step 470 where the
analog audio signal is converted through an ADC to a digital
signal. Additional filtering and/or signal conditioning may be
applied here. The process then proceeds to step 450 where timing
information is extracted if it has been embedded with audio
segments. Otherwise in the case of digital wireless audio being
transmitted, the process proceeds to step 430. If step 340 was not
included in method 300 for the microphone module 100, the process
proceeds to step 440. Otherwise, the demodulated data is checked
for errors and/or the presence of errors is detected. At this
point, information may be gathered regarding the quality of signal
(such as RSSI, SNR and/or error rate data) and such information may
be included in audio data subsequently forwarded to the receiver
hub 105. Upon reaching step 440, if step 330 was not included in
method 300, the process forwards to step 450. Otherwise, the data
may be optionally decompressed, extracting the original (PCM) raw
digital data that was produced by step 320 of method 300. At step
450, timing information may be detected and the process proceeds to
step 451, where quality of information (such as RSSI or SNR) may be
added into the data. Other functions at step 451 may include muting
data samples or setting them to an identifiable pattern for
sections of the audio waveform where data samples are known to be
corrupt. Upon reaching step 452, data is encoded into packets based
on the DANTE protocol (Layer 3 packets), or another audio over
Ethernet protocol. Other data packets may be created that also
contain information reported regarding the number and location of
error detected, wireless signal levels, noise levels and any other
information the base stations can provided that may prove useful to
the receiving hub 105. The process then proceeds to step 460 where
the data packets are transmitted (or broadcast) over the second
stage 116 of the network.
[0036] FIG. 5 is a block diagram showing select steps that may be
taken for receiving, audio data from each base station by a
receiver hub and processing that data before forwarding it to an
end-point according to an exemplary embodiment. It should be
understood that multiple modalities exist for the reconstruction of
audio data within the receiver hub: For example, as a first
modality, reconstruction may be based on sample selection, wherein
data samples are repeatedly constructed on a sample to sample basis
emphasizing data received by receiver base stations that are deemed
as being the most reliable at the time of reception. As a second
modality, each receiver base station may further process its own
received data such that unreliable data will later have a minimal
impact on reconstruction. For example, at times when data reception
is deemed as unreliable, it may simply mute corresponding audio
data or set it to values known to signify unreliable data, such as
full-scale values that would be omitted by outlier rejection
protocols. As an example of a third modality, redundancy in time
may be used. In this case, the microphone module stores data from
previous time periods in memory and retransmits data from the
previous time periods in the same or different stream as the live
data so that the retransmitted data can be used in case the data
was not reliably received when it was first transmitted. For
example, the microphone module 201 may transmit the most recently
received data in real time as well as data received after being
passed through a delay buffer (such as preferably less than a 100
ms in length or more preferably less than 30 ms). Since it is
preferred that the receiver hub continually receive all data
transmitted by each receiver base station, it may still reconstruct
sections of missing audio if time periods are detected where
receipt of all receiver data has been flagged as unreliable. While
it is preferred that all the data be transmitted to the receiver
hub in this modality, it is possible for the receiving base
stations be used to determine whether it is necessary to use the
retransmitted audio data and/or used to substitute the
retransmitted data.
[0037] At step 510 of method 500, the receiving station 105
receives data packets, preferably compatible with the DANTE
protocol and retrieves audio data and other information relating to
signals, errors, error rates, noise or any other information
forwarded by the base stations. Proceeding to step 515, timing
information relating to audio segments is retrieved. Regardless of
whether or not timing information such as time-stamps has been
included with audio segments, the relative timing between received
segments of audio waveform data may be inferred by computing the
cross-correlation between waveform segments and detecting a peak in
the cross-correlation function to indicate an alignment offset
between the two segments. The lag corresponding to this peak may
correspond to the timing difference between them and subsequently
be used to align them prior to combining them at step 520. The
process proceeds to step 520. At this step, for each channel of
audio, where each microphone module 101 will be assigned to a
distinct channel, audio data is combined, selected and/or augmented
as described above in connection with the various modalities of
reconstruction, in order to produce the most robust, the highest
resolution and/or lowest noise level for each resultant audio
output data stream. Once reconstruction has occurred, the process
then proceeds to step 530. In many cases this step may be skipped.
However, in some embodiments, the receiver hub 105 may operate on
data before it is fully decoded. For example, data may be encoded
using a low delay audio compression technique (for example, the
aptX Live audio codec, low-delay AAC, Siren, etc.) for reducing
bandwidth requirements of the wireless transmission. In some cases
where digital transmission is used, it may be desirable to blend
selections from within data segments to produce a error-free (or
reduced error) segments before attempting to decompress the audio
signal. At step 535, missing or corrupt data may be repaired (if
required) via synthesis through a packet-loss-concealment
algorithm. These types of algorithms may be used to synthesize
missing portions of audio data as described above. The process
proceeds to step 540 where the resultant output data stream is
provided, sent or broadcast to one or more end-points.
[0038] FIGS. 3-5 illustrate methods according to example
embodiments. Although specific orders of steps are suggested among
these figures, these are by no means the only order that may prove
suitable for the embodiments disclosed here. For example, in many
cases, two or more steps may be performed concurrently or with
partial concurrence and/or in reverse order or omitted.
Furthermore, many additional steps are implied, although not shown,
to achieve the functions described here and as being evident to one
skilled in the art, are considered part of this disclosure. Many
variations may depend on the software and/or hardware systems
chosen for a specific embodiment. Upon reading this disclosure,
these variations will become evident to one skilled in the art and
are to be considered as suggested and envisioned within the scope
of the disclosure.
[0039] FIG. 2 shows a system 200 constructed in accordance with
another exemplary embodiment of the invention. In contrast to the
system 100 of FIG. 1, the system of FIG. 2 illustrates the use of
multiple microphone modules 201A and 201B connected to respective
transmitters 202A and 202B for wirelessly communicating data to
three wireless receivers 204A, 204B and 204C in base stations 203A,
203B and 203C respectively. In a similar manner to the system 100
in FIG. 1, the transmitters 202A and 202B that are
electromagnetically coupled to receivers 104A, 104B and 104C may be
construed as comprising the first stage 215 of a network.
[0040] In the second stage 216 of the network, each of the three
base stations 203A, 203B and 203C may be serially linked (or "daisy
chained"). In this topology, the third base station 203C is linked
by communication link 209C to the second base station 203B, that is
linked by communications link 209B to the first base station 203A,
that is linked by communications link 209A to the receiver hub 205.
With this topology, each base station in addition to receiving
wireless audio data and forwarding (or broadcasting) this data the
next base station or receiver hub 205 must also forward audio data
received by it from the opposing base station toward the receiver
hub 205.
[0041] In other embodiments, either two of more than three base
stations may be serially connected from the receiver hub. In some
embodiments, more than one daisy chain of serially connected base
stations may emanate from the receiver hub 205. Alternative
embodiments envisioned in the scope of this disclosure includes
those where the network topology for the second stage 216 of the
network may include any combination of communications links such
that each base station has a pathway present whereby audio data
received by it may broadcast such that it is forwarded along some
path to the receiver hub 205. Again, the preferred means of
providing communication links between base station and the
receiving hub is Ethernet, while the preferred data format for
broadcast is DANTE. With this design, an arbitrary number of base
stations may be connected along each daisy chain emanating from the
receiver hub 205.
[0042] Like in the system 100 of FIG. 1, each base station receives
audio from microphone module 201A via its microphone transmitter
202A. However, each base station may also receive audio data from a
second microphone module 201B via its microphone transmitter 202B.
In other embodiments, more than two microphone modules may
wirelessly transmit audio data to be received by the base
station.
[0043] In cases where multiple microphone modules are wirelessly
transmitting audio data to the base stations, each microphone
module will need to be configured to transmit on its respective
channel and each base station receive will need to be configured to
receive wireless audio data on the corresponding channels.
Furthermore, each microphone module need not be identical for the
application of this invention. As can be seen from FIG. 2, one
microphone module 201A is depicted as an integrated unit, while the
other microphone module is depicted as being a lavalier type
element 214 with a body pack transmitter 210 integrated with its
microphone transmitter 202B. In some embodiments, base stations may
even be configured to receive multiple wireless transmission
formats from different types of microphone modules, including
mixing analog and digital.
[0044] Since the base stations 103A, 103B and 103C are receiving
multiple channels of wireless audio data, each channel of data is
processed in the receiving base station separately with respect to
its channel. Similarly to the single microphone module system 100,
base stations in the multiple microphone module system 200 may each
reformat the received data, preferably into a DANTE compatible
protocol and broadcast this data through the second stage 216 of
the network to the receiver hub 205. Upon receiving this data, the
receiver hub 205 may then process each channel independently,
generating an output data stream corresponding to each microphone
module. The details for processing the received audio for each
channel may be similar to that for the single microphone module
case. Like in the system 100 of FIG. 1, the system 200 of FIG. 2
provides one or more of the reconstructed output or output data
streams to an end-point that may include the use of a
mixer/recorder 206, broadcast network 207 and/or playback devices
208.
[0045] The second stage 216 of the network may also be used for
interfacing a user interface 217 for communicating command, control
and configuration information to ether the receiver hub and/or base
stations. This is particularly apparent when the second stage 216
of the network is based on and Ethernet connection. In these cases,
the user interface 217, is preferably based on a computer and
supporting software can serve as an interface to users for
embedding command, control and configuration information into (or
broadcasting this information to) any selected device connected to
the second stage 216 of the network. In alternative embodiments,
other forms of a user interface may suffice, and these may include
the use of smart phones or other handheld computing devices. The
second stage 216 of the network also provides a communication path
for status information from either the receiver hub 205 or any base
station to be sent back to the user interface 217.
[0046] If a sufficient computing power is present on the user
interface 217, this unit may also assume the functions associated
with the receiver hub 215, essentially merging the operation of the
user interface 217 and receiver hub 205 into a single unit. The
user interface may itself also contain large amount of disk storage
and also assume the roll of an end-point for recording, playback
and/or mixing and in some embodiments may itself aid in the
broadcast of the output data stream to other end-points.
* * * * *